MOLECULAR-BASIS OF TYPE-I (TYROSINASE-RELATED) OCULOCUTANEOUS ALBINISM - MUTATIONS AND POLYMORPHISMS OF THE HUMAN TYROSINASE GENE

Type I (tyrosinase related) oculocutaneous albinism (OCA) results from mutations of the tyrosinase gene on chromosome 11 q that lead to redu ced or absent melanin pigment synthesis. The phenotype of Type I OCA i s broad, ranging from a total lack to only a moderate reduction of mel anin, and the phenotypic variation is associated with different mutant alleles at the tyrosinase locus. A total of 36 mutations have been id entified in Type I OCA including 24 missense, 4 nonsense, and 8 frames hift mutations. The majority of affected individuals have been compoun d heterozygotes with different maternal and paternal alleles. Six poly morphic sites for haplotype analysis have been identified in the tyros inase gene including 2 in the promoter region, 2 in the coding region associated with alternative amino acids in the protein, and 2 RFLPs in the first intron.